Precise environmental interpretation of Colorado Plateau eolian sandstone bodies remains difficult despite advances in sedimentology. The early interpretation of all sediments of great textural and compositional maturity, and high grain roundness and frosting, that display large-scale cross-lamination as desert deposits has hindered environmental reconstruction. Great sandstone wedges that thicken away from the cratonic margin, such as the vast Navajo-Nugget complex, are particularly enigmatic.

Colorado Plateau eolian sediments represent combinations of four environmental models: mainly eolian, mainly marine, mixed alluvial-eolian, and mixed littoral-eolian. Mainly eolian units (Coconino, Cow Springs) are recognized by limited areal extent, irregular deposit geometry, intricate cross-bedding, lack of prominent planar features, and by scarce paleontologic evidence. Mainly marine units formerly considered to be eolian (Cedar Mesa, White Rim, Glorieta) are characterized by horizontal bedding, lower angle and less intricate cross-bedding, certain stratigraphic relations, and a few marine fossils. Mixed alluvial-eolian sediments (Wingate, lower parts of Navajo) have complex lateral and vertical facies relations with adjacent alluvial units and show evidence of fluvial modificatio .

Mixed littoral-eolian deposits (De Chelly, Navajo, Entrada) are areally extensive, bear multiple parallel-truncation planes as prominent features, and generally are well cross-bedded (but contain some horizontal or aqueous ripple bedding). Contorted slump structures and thin discontinuous carbonate lentils are conspicuous in some units. Partial intertonguing with marine units, although generally obscure, is characteristic. Parallel truncation planes are produced by repeated widespread marine planation of coastal dune fields by temporary transgressive oscillations, followed by varying degrees of deflation removal of water-laid beds after subsequent reexposure. Mixed littoral-eolian deposits

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require a tectonic-climatic-environmental model which has no definite modern analog; this causes difficult interpretational problems.

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